Proteins are complex macromolecules composed of amino acid residues covalently bonded by peptide bonds. Each protein contains at least primary, secondary, and tertiary structures. Only some proteins also have quaternary structures. The primary structure consists of linear chains of amino acids. Proteins are first synthesized as primary sequences, then folded into secondary structures, then tertiary structures, and finally quaternary structures. The secondary structure contains regions of amino acid chains stabilized by hydrogen bonds from the polypeptide backbone. The α-helix and the β-sheet are two main types of secondary structure. Tertiary structure is the three-dimensional (3D) structure of a protein molecule and is the intramolecular arrangement of secondary structure. 3D structural analysis is important for understanding the function of proteins at the molecular level. The quaternary structure affects the 3D shape of a protein and is formed through side-chain interactions between two or more peptides.

Proteins are widely present in nature, and their sources can be plant, animal, human, and microorganism. Extracts obtained from these sources contain contaminants such as bacteria, viruses, and nucleic acids in addition to the presence of target proteins. Therefore, in the purification, all molecules and structures except desired proteins should be removed. The selection of an optimal purification method should take into account the characteristics of the protein such as size and shape, total charge, hydrophobic groups on the surface, and the binding capacity with the stable phases used.

Proteins play crucial roles in almost all biological processes, including DNA replication, transporting molecules, catalyzing metabolic reactions, and providing structural support to cells. Due to key roles of proteins, it is important to study their structure, synthesis, function, and regulation by molecular biochemical methods. In a protein chain, the number, chemical structure, and order of amino acid sequences determine the structure and chemical behavior of the protein. The first step in the identification of protein structure is to determine its amino acid composition. The two major direct methods for protein sequencing are Edman degradation (N-terminal sequencing) and mass spectrometry. The higher order structure of a protein can be determined by technologies such as circular dichroism, nuclear magnetic resonance spectroscopy, x-ray crystallography, and electron microscopy. Protein quantification is often necessary prior to extraction, isolation, and analysis of protein samples. There are a variety of methods for protein quantification including UV absorptiometry, reagent-based assays (such as Bicinchoninic acid, Bradford or Coomassie brilliant blue, and Lowry assays), and immunodetection techniques (such as enzyme linked immunosorbent assay, Western blot analysis, reverse phase protein array, and immunohistochemistry).

Amerigo Scientific offers reliable reagents and convenient kits for the extraction, purification, enrichment, identification, conjugation, and analysis of proteins.

Protein Purification

Protein Conjugation and Labeling

Protein Analysis and Characterization

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